Hello, can anybody explain why the following code compiles with -version=works but not without?

module test;

import std.stdio;

abstract class Parent
{
	int opApply(int delegate(ref int) dg)
	{
		int fakeDelegate(ref uint fake, ref int content)
			{ return dg(content); }
		return opApply(&fakeDelegate);
	}

	abstract int opApply(int delegate(ref uint, ref int) dg);
}

class Child : Parent
{
	override int opApply(int delegate(ref uint, ref int) dg)
	{
		uint index = 0;
		for(int content = 1; content < 6; content++)
		{
			int result = dg(index, content);
			if(result != 0)
				return result;
			index++;
		}
		return 0;
	}
}

void main()
{
	version(works)
		Parent child = new Child();
	else
		Child child = new Child();
	foreach(int content; child)
		writefln(content);
}

I'm making some collection classes and had the same problem. It seems like for some reason the compiler can't match the index-free foreach() in the child, but can in the parent. It obviously knows it's there, or else it wouldn't compile because the index-free opApply would be abstract. Any thoughts?

Apparently I'm missing some basic concept  about how D does OO since I recreated the problem with a simpler function. I'll re-examine things...

On Fri, 03 Jul 2009 17:42:45 -0400, Mike L. <sgtmuffles@myrealbox.com> wrote:

> module test;
>
> import std.stdio;
>
> abstract class Parent
> {
> 	int opApply(int delegate(ref int) dg)
> 	{
> 		int fakeDelegate(ref uint fake, ref int content)
> 			{ return dg(content); }
> 		return opApply(&fakeDelegate);
> 	}
> 	
> 	abstract int opApply(int delegate(ref uint, ref int) dg);
> }
>
> class Child : Parent
> {

/* add this line (see http://www.digitalmars.com/d/2.0/function.html#function-inheritance) */
alias Parent.opApply opApply;

> 	override int opApply(int delegate(ref uint, ref int) dg)
> 	{
> 		uint index = 0;
> 		for(int content = 1; content < 6; content++)
> 		{
> 			int result = dg(index, content);
> 			if(result != 0)
> 				return result;
> 			index++;
> 		}
> 		return 0;
> 	}
> }
>
> void main()
> {
> 	version(works)
> 		Parent child = new Child();
> 	else
> 		Child child = new Child();
> 	foreach(int content; child)
> 		writefln(content);
> }